In comparison with Long Term Evolution (LTE), a higher carrier frequency is used in a 5G communications system. A current standard stipulates that a high frequency is usually above 6 GHz, and a currently most researched band is 28 GHz, 38 GHz, 72 GHz, or the like, to implement wireless communication with higher bandwidth and a higher transmission rate. However, in comparison with conventional low-frequency communication, a high frequency system has more serious intermediate radio frequency distortion, especially impact of phase noise. In addition, impact of a Doppler shift and a carrier frequency offset (CFO) increases with a frequency.
In an example of multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM), both phase noise and a carrier frequency offset of a receive end and those of a transmit end are considered, and a reception expression of an nth receive antenna on a kth subcarrier after the receive end performs fast Fourier transform (FFT) is:
            Y      n      k        =                            ∑                      m            =            1                    M                ⁢                              H            nm            k                    ⁢                                                    P                n                                  r                  ,                  0                                            ⁢                              P                m                                  t                  ,                  0                                                                    ︸              CPE                                ⁢                      S            m            k                              +                                    ∑                          m              =              1                        M                    ⁢                                    ∑                              i                =                0                                            K                -                1                                      ⁢                                          P                n                                  r                  ,                                                            (                                              k                        -                        i                                            )                                        ⁢                    K                                                              ⁢                              H                nm                i                            ⁢                                                ∑                                                            l                      =                      0                                        ,                                                                                                                        l                            ≠                            i                                                    &                                                ⁢                        l                                            ≠                      k                                                                            K                    -                    1                                                  ⁢                                                      P                    m                                          t                      ,                                              (                                                  i                          -                          l                                                )                                                                              ⁢                                      S                    m                    l                                                                                                ︸          ICI                    +              Z        n        k              ,          ⁢          ⁢            where      ⁢                          ⁢              P        n                  r          ,          k                      =                  1        K            ⁢                        ∑                      t            =            0                                K            -            1                          ⁢                              e                          j              ⁢                                                          ⁢                                                θ                  n                  r                                ⁡                                  (                  t                  )                                                              ⁢                      e                          j              ⁢                                                          ⁢              2              ⁢              π              ⁢                                                          ⁢                              tk                /                K                                                          ,            P      m              t        ,        k              =                  1        K            ⁢                        ∑                      t            =            0                                K            -            1                          ⁢                              e                          j              ⁢                                                          ⁢                                                θ                  m                  t                                ⁡                                  (                  t                  )                                                              ⁢                      e                          j              ⁢                                                          ⁢              2              ⁢              π              ⁢                                                          ⁢                              tk                /                K                                                          ,namely:
            P      n              r        ,        0              =                  1        K            ⁢                        ∑                      t            =            0                                K            -            1                          ⁢                  e                      j            ⁢                                                  ⁢                                          θ                n                r                            ⁡                              (                t                )                                                          ,            P      m              t        ,        0              =                  1        K            ⁢                        ∑                      t            =            0                                K            -            1                          ⁢                              e                          j              ⁢                                                          ⁢                                                θ                  n                  t                                ⁡                                  (                  t                  )                                                              .                    
Hnmk represents a channel from an mth transmit antenna to the nth receive antenna on the kth subcarrier, Smk in represents data sent by using the mth transmit antenna on the kth subcarrier, Znk represents noise of the nth receive antenna on the kth subcarrier, Pnr,k represents a phase deviation caused by the phase noise and the CFO of the receive end for the nth receive antenna on the kth subcarrier, and Pnt,k represents a phase deviation caused by the phase noise and the CFO of the transmit end for an mth transmit antenna on the kth subcarrier. It can be learned from the expression that impact of phase noise on OFDM performance is mainly reflected in two aspects: a common phase error (CPE) and inter-carrier interference (ICI), and impact of CFO on OFDM performance is mainly reflected in ICI. In an actual system, the impact of the ICI on the performance is less than the impact of the CPE on the performance. Therefore, the CPE is preferentially compensated for in a phase noise compensation scheme.
FIG. 1A shows a constellation point at which a 64QAM modulation signal is not affected by phase noise. FIG. 1B shows a constellation point at which a 64 quadrature amplitude modulation (QAM) signal on a 2G band is affected by phase noise. FIG. 1C shows a constellation point at which a 64 QAM modulation signal on a 28G band is affected by phase noise. As shown in FIG. 1A to FIG. 1C, phase noise is used as an example, and a phase noise level deteriorates with a band at a level of 20×log(f1/f2). A 2G band and a 28G band are used as an example, and a phase noise level of the 28G band is higher than that of the 2G band by 23 dB. A higher phase noise level causes greater impact of a common phase error, and the CPE causes a bigger phase error.
A CPE imposes same impact on different subcarriers of a same OFDM symbol, and phase errors on the different subcarriers are different because of white Gaussian noise. Therefore, in frequency domain, a specific quantity of phase compensation reference signals (PCRS) needs to be used to estimate the CPE and calculate an average, to reduce impact of the white Gaussian noise as much as possible. PCRS may also be referred to as phase tracking reference signals (PTRS). PCRS is not uniformly named currently in the industry, but is uniformly referred to as the PTRS subsequently for convenience in the present disclosure.
Currently, how to determine transmit power of a PTRS is a technical problem that needs to be urgently resolved.